Robert Einhorn, the State Department's special adviser for nonproliferation and arms control, says Washington is not now directing its efforts toward changing the regime that governs Iran.

"We may not like this regime in Tehran -- in fact, we don't like this regime in Tehran -- but we believe that this regime will be changed when Iranian people decide it needs to be changed, and by the Iranian people," Einhorn says.

Einhorn says U.S. policy is aimed at changing Iran's behavior concerning its nuclear activities, its human rights record, and what he describes as Iranian support for terrorist groups.

Einhorn's comments came during the first day of the Carnegie Endowment's International Nuclear Policy Conference in Washington on March 28, which has brought together officials and experts dealing with nuclear issues and nonproliferation.